Various architectural forms based on the concept of assembly are emerging one after another, but at the current stage, especially in civil buildings, reinforced concrete structures still occupy the absolute mainstream. As the main component of prefabricated concrete structure buildings, the design, production, supply, quality and even the later maintenance of prefabricated concrete components have also attracted more and more attention.
Prefabricated concrete components are not new products. They were once popular in my country from the 1950s to the 1980s. However, with the development of society, people's demand for beautiful products and changes in construction methods have also put forward new requirements for prefabricated concrete components. For example, prefabricated components must not only meet the requirements of architecture and structure but also meet the requirements of construction, equipment installation, aesthetics, energy saving, etc. The society's requirements for prefabricated concrete components for prefabricated buildings are getting higher and higher. On the other hand, with the development of materials science and concrete processing technology in recent years, prefabricated concrete components can present various forms that were previously unimaginable, such as light transmission, bending, heat preservation, and even power generation, which also provides possibilities for the diversity of prefabricated buildings.
This article sorts out and displays pictures of the prefabrication technology of modern concrete components from the perspective of the finish, shape, material, and function of prefabricated components, and provides research results and a practical basis in the development process for the industry to achieve the goal of "innovating prefabricated concrete technology to help high-quality engineering construction".
Prefabricated Component Finishes Are More Enriched
1. Facing Brick Finish
In the processing of prefabricated components with facing brick finishes, it is generally necessary to adopt a reverse one-time forming process, that is, first divide the finish into reasonable units according to the component finish distribution drawing, and then make the facing brick set mold according to this unit, and make the facing brick into a facing brick set. After the component mold is assembled, the facing brick set is laid on the mold, and then the component is formed according to the process. After demolding, the surface of the component-facing brick can be cleaned.
2. Stone Finish
The reverse process generally produces prefabricated exterior wall panels with granite stone finishes. The thickness of granite is generally 2.5 to 3.0 cm. Due to the porous structure of granite, to prevent alkaline substances in concrete from penetrating the surface of the stone and causing surface pollution, the back of the stone needs to be sealed. At the same time, to enhance the bonding strength between the stone and concrete, a 45-degree inclined hole needs to be drilled on the back of the stone and stainless steel hooks need to be installed. The specimen pull-out and shear tests should determine the number of hooks.
3. Paint Finish
In the processing of paint-finished components, the paint is generally applied after the components are completed. The paint is generally divided into exterior wall waterproof paint and metal paint. For exterior wall waterproof paint, the coating is thicker and the surface requirements of concrete components are not high. However, metal paint has a thin coating and a metallic texture. If the surface of the component is slightly uneven, it will be reflected immediately after the paint is applied, affecting the appearance. During the production process, special attention should be paid to the flatness of the surface and the quality of the joints, and there are also higher requirements for the repair quality of the product.
4. Exposed Aggregate Finish
Water washing is also called retarding technology. By applying the retarder, a cement retarding layer is formed on the concrete surface. After the component is cured, it is washed with high-pressure water to expose the aggregate on the concrete surface.
Sandblasting technology uses high-pressure shot blasting to spray the concrete surface so that the cement slurry on the concrete surface is partially peeled off and the aggregate is exposed.
Prefabricated Component Modeling Is More Personalized
With the architect's pursuit of personalized architectural modeling, some forms and shapes can no longer be satisfied by on-site casting, and can only be prefabricated in factories. However, in component processing, based on the characteristics of concrete materials and molds, some shapes are also difficult to process in traditional ways, such as curved surfaces and no demoulding slopes. Therefore, we generally use composite mold technology, special rubber molds to ensure the shape of components, and steel molds to ensure the strength and rigidity of molds, to realize the production of various modeling components.
1. Recycled concrete component production technology
With the strengthening of national ecological environmental protection efforts, natural resource mining has been restricted, the utilization of industrial and construction waste has received more and more attention, and the application of recycled aggregate concrete has become more and more extensive, but recycled concrete has not been used in the field of prefabricated components.
2. Ultra-high-performance concrete component production technology
Ultra-high-performance concrete (active powder concrete) has been developed for more than 40 years. It can achieve a minimum water-cement ratio of 0.14 and provide the maximum density and strength.
It has ultra-high mechanical properties: compression resistance of 200MPa, flexural resistance of 25MPa, tensile resistance of 10MPa, elastic modulus of 50GPa, and fracture toughness of 20KJ.
Because it has ultra-high durability: high density, basically no possibility of carbonization corrosion, concrete form is no longer rigid, lighter weight, thin plate structure, hollow area can be as high as 60% or more, the minimum can achieve 30kg/m2 (calculated as 3cm thick), curved surface modeling is easier to achieve, construction efficiency is higher, cost is lower, and durability is better. Compared with metal, fiberglass, and other materials, concrete has lower construction costs, is easier to construct over a large area, has higher assembly efficiency, and provides better durability and lower maintenance costs.
3. High-performance concrete component production technology
With the rapid development of super-high-rise buildings in my country, the requirements for weight reduction energy conservation, and emission reduction of concrete structures are becoming higher and higher, and the strength requirements of concrete materials are also becoming higher and higher. Foreign advanced structural component concrete has generally used C60, and C100~C120MPa concrete is widely used in super-high-rise buildings.
We cooperated with Tongji University to carry out experimental research on the C100 concrete frame structure of prefabricated buildings. Starting from mix design, raw material selection, and preparation process, we carefully organized and achieved the expected results, with an actual average strength of 122MPa.
The Functions Of Prefabricated Components Are More Diversified
1. Prefabricated Component Information Application Technology
(1) Before the production of concrete prefabricated components, the management personnel will issue RFID chips to the actual prefabricated component production factory according to the number of components in the project contract information, and the daily chip usage can be queried in the ERP management system.
(2) After receiving the chip, the prefabricated component production factory will make the chip one day before the component production according to the production plan, and each chip corresponds to a component. The printed information includes: project name, plate number, volume, concrete strength and QR code (the QR code only provides basic information of the chip, and detailed information of the component is obtained by scanning the built-in global unique code of the chip).
At present, various electronic components can also be buried in the prefabricated components to detect and transmit the stress and strain of the components in real time, which greatly facilitates the maintenance and monitoring of the building.
2. Photovoltaic Integrated Component Production Technology
Solar photovoltaic building integration (BIPV) is to combine photovoltaic power generation with buildings, and photovoltaic devices are arranged on the surface of the building's outer structure to generate electricity, so that "buildings generate green energy". Because it combines the beauty of architecture and the many advantages of photovoltaic utilization, it has become a very advanced high-tech technology, widely circulated around the world, and will also become a new trend in the field of photovoltaic applications.
In general, the rapid development of prefabricated buildings has put forward higher requirements for prefabricated building components. At the same time, after nearly a decade of development, our prefabricated components have made great progress in terms of materials, shapes, functions, etc., providing a solid foundation for the diversification of our buildings.
